Method for delivering a volatile material

ABSTRACT

A method of delivering a volatile material to the atmosphere in a continuous manner is disclosed. The method includes providing a delivery engine having a reservoir that includes a volatile material mixture. The volatile material mixture includes about 40% to about 100%, by total weight, of the volatile materials each having a vapor pressure at 25° C. of less than about 0.1 torr. The delivery system also includes a microporous membrane enclosing the reservoir, wherein the microporous membrane comprises an average pore size of about 0.01 to about 0.03 microns.

FIELD OF THE INVENTION

The present invention relates to a method for delivering a volatilematerial to the atmosphere in a continuous manner.

BACKGROUND OF THE INVENTION

It is generally known to use a device to evaporate a volatile materialinto a space, particularly a domestic space, in order to deliver avariety of benefits, such as air freshening or perfuming of the air.Non-energized systems, for example, systems that are not powered byelectrical energy, are a popular way for the delivery of volatilematerials into the atmosphere. These systems can be classified intothose that require human actuation, such as aerosols, those which do notrequired human actuation such as wick based systems and gels. The firsttype delivers the volatile materials on demand and the second type in amore continuous manner.

U.S. Pat. No. 4,161,283 discloses an article for delivering a volatilematerial comprising a reservoir, polymeric sheet or membrane, and abarrier layer releasably bonded to the outer wall of the reservoir. Onedrawback with this type of article is its susceptibility tode-lamination and leakage because the volatile material is in contactwith the membrane during storage or non-use. Another drawback may bethat volatile materials build up in the membrane during storage,resulting in a spike in intensity immediately after the barrier layer isremoved. Another drawback may be that the peel force makes it isdifficult to remove the barrier layer without damaging the polymericsheet or membrane. Yet another drawback may be the selectivity of themembrane in that it does not easily allow low vapor pressure volatilematerials to diffuse through the polymer.

U.S. Pat. No. 4,824,707 discloses a decorative air freshener unit havinga capsule containing a supply of volatile fragrance. The capsule istrapped between a microporous sheet and a backing sheet. The capsule isruptured by applied force and the released fragrance is absorbed intothe microporous sheet which gradually exudes the fragrance. Thisapproach may limit the longevity of a scent since liquid is released allat once to the microporous sheet, and there is little control over themanner in which the liquid will wet the microporous sheet.

As such, there exists a need for a method for delivering, over a periodof time, a continuous release of volatile materials having a broad rangeof molecular weights and vapor pressures.

SUMMARY OF THE INVENTION

According to one embodiment of the invention, there is provided a methodof delivering a volatile material to the atmosphere in a continuousmanner. The method includes the step of providing a delivery systemhaving a reservoir that includes a volatile material mixture. Thevolatile material mixture includes about 40% to about 100%, by totalweight, of volatile materials each having a vapor pressure at 25° C. ofless than about 0.1 torr. The delivery system also includes amicroporous membrane enclosing the reservoir, wherein the microporousmembrane comprises an average pore size of about 0.01 to about 0.03microns.

According to another embodiment of the invention, there is provided amethod of delivering a volatile material comprising the steps ofproviding a delivery engine comprising a reservoir containing a volatilematerial, a rupturable substrate enclosing the reservoir, a microporousmembrane enclosing the reservoir and the rupturable substrate, a ruptureelement positioned between the rupturable substrate and the microporousmembrane; and compressing the microporous membrane and the ruptureelement to breach the rupturable substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with the claims particularly pointingout and distinctly claiming the invention, it is believed that thepresent invention will be better understood from the followingdescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 shows a perspective view of one embodiment of an apparatus of thepresent invention.

FIG. 2 shows an exploded, perspective view of one embodiment of adelivery engine in accordance with the present invention.

FIG. 3 shows a cross-sectional view of another embodiment of a ruptureelement in accordance with the present invention.

FIG. 4 shows a cross-sectional view of another embodiment of a ruptureelement in accordance with the present invention.

FIG. 5 shows a side elevational view of the delivery engine in FIG. 2 inaccordance with the present invention.

FIG. 6 shows a front elevational view of one embodiment of a housing inaccordance with the present invention.

FIG. 7 shows a top plan view of the housing in FIG. 6.

FIG. 8 shows a cross-sectional view along lines 8-8 of the apparatus inFIG. 1.

FIG. 9 shows the cross-sectional view in FIG. 8 where the deliveryengine is being received by the housing.

FIG. 10 is a graph showing evaporation profiles of volatile materialshaving varying vapor pressure ranges evaporated from a microporousmembrane in accordance with the present invention

FIG. 11 is a graph showing evaporation profiles of volatile materialsevaporated from a polyethylene membrane and from a microporous membranein accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an apparatus for the delivery of avolatile material to the atmosphere. It is contemplated that theapparatus may be configured for use in a varierty of applications todeliver volatile materials to the atmosphere.

For example, the apparatus may be configured for use with an energizeddevice. An exemplary energized device may be an electrical heatingdevice. More particularly, the device may be an electrical wall plug airfreshener as described in U.S. Pat. No. 7,223,361; a battery poweredheating device; or other heating devices (e.g. devices powered bychemical reactions such as catalyst fuel systems; solar powered devices,etc.). In such devices, the volatile material delivery engine may beplaced next to the heating surface to diffuse the volatile material. Thevolatile material formula may be adjusted to include an overall lowervapor pressure formula.

The apparatus may also be configured for use with an air purifyingsystem to deliver both purified air and volatile materials to theatmosphere. Non-limiting examples include air purifying systems usingionization and/or filtration technology for use in small spaces (e.g.bedrooms, bathrooms, automobiles, etc.), and whole house central airconditioning/heating systems (e.g. HVAC).

The apparatus may also be configured for use with an aerosol ornon-aerosol air spray. In this embodiment, the delivery engine candeliver volatile materials upon user demand or programmed toautomatically deliver volatile materials to the atmosphere.

The apparatus may also be configured for use with a fan to delivervolatile materials to the atmosphere.

For purposes of illustrating the present invention in detail, theinvention is described below in a non-energized system. “Non-energized”means that the apparatus is passive does not require to be powered by asource of external energy. In particular, the apparatus does not need tobe powered by a source of heat, gas, or electrical current, and thevolatile material is not delivered by aerosol means.

In the non-energized embodiment, the apparatus of the present inventiondelivers a volatile material in a substantially continuous manner whenthe apparatus is in a resting position (i.e. the apparatus is not beingmoved). The emission level of volatile materials may exhibit a uniformintensity until substantially all the volatile materials are exhausted.The continuous emission of the volatile materials can be of any suitablelength, including but not limited to, up to: 20 days, 30 days, 60 days,90 days, shorter or longer periods, or any period between 30 to 90 days.

The apparatus of the present invention is suitable for purposes ofproviding fragrances, air fresheners, deodorizers, odor eliminators,malodor counteractants, insecticides, insect repellants, medicinalsubstances, disinfectants, sanitizers, mood enhancers, and aromatherapyaids, or for any other purpose using a volatile material that acts tocondition, modify, or otherwise change the atmosphere or theenvironment. For purposes of illustrating the present invention indetail, but without intending to limit the scope of the invention, theinvention will be described in an air freshening system for deliveringliquid containing perfume raw materials.

Referring to FIG. 1, an apparatus 10 in accordance with the presentinvention is shown. The apparatus 10 includes a delivery engine 100 anda housing 200.

Delivery Engine

Referring to FIG. 2, the delivery engine 100 comprises a width, lengthand depth along the x-axis, y-axis, and z-axis axis, respectively. Thewidth, length, and depth may be such that the delivery engine 100 isconsidered compact and/or portable. By “compact” or “portable”, it ismeant that the delivery engine 100 can be conveniently and comfortablycarried in a pocket, purse, or the like. The delivery engine 100 can beconstructed as a disposable, single-use item or one that it isreplenished with a volatile material.

The delivery engine 100 may include a lip 102 that defines the outerperimeter of the delivery engine 100 and may circumference a reservoir110 for containing a volatile material as well as a collection basin112. The delivery engine 100 may also include a rupturable substrate 120secured to the reservoir 110; a rupture element 130 positioned adjacentto the rupturable substrate 120; and a microporous membrane 140 securedto the lip 102 and enclosing the rupturable substrate 120, reservoir110, and collection basin 112.

The body 104 of the delivery engine 100 can be thermoformed, injectionmolded, or blow molded with any known material. In some embodiments, thebody 104 includes all structural aspects of the delivery engine 100minus the rupturable substrate 120, the rupture element 130, andbreathable membrane 140. In other embodiments, the body 104 includes therupture element 130. The body 104 may be made of a multi layer materialwhich may include a barrier layer to prevent evaporation of a volatilecomponent and at least one outer layer that allows a rupturablesubstrate 120 to be heat-sealed to the body 104. A suitable sealantlayer would include a layer of polyethylene or polypropylene or anysuitable polyolefin sealant that allows for a leak proof seal of thereservoir 110. Suitable materials to form the body 104 of the deliveryengine 100 include plastics, such as Pentaplast Pentaform® 2101available from Klockner. In some embodiments, the material is colored ornon-colored see-through plastic. The see-through material permitsobservation of the liquid and end-of life.

Reservoir

The delivery engine 100 may comprise a reservoir 110 for holding avolatile material. The reservoir 110 may have a width, length and depthalong an x-y-z axis, respectively. The reservoir 110 may be elongate inthat its width to length ratio is about 2:1 to 4:1, alternatively 1.5:1to 2.5:1. The reservoir 110 may have a width of about 45 mm to about 55mm, alternatively about 51 mm; a length of about 15 mm to about 30 mm toabout, alternatively about 23 mm; a depth of about 5 mm to about 15 mm,alternatively about 11 mm. The dimensions of the reservoir 110 may besuch that it holds about 2 ml to about 50 ml of liquid containing avolatile material. Alternatively, the reservoir 110 may hold about 2 mlto about 30 ml, alternatively about 2 ml to about 10 ml, alternativelyabout 2 ml to about 8 ml, alternatively about 4 ml to about 6 ml,alternatively about 2 ml, alternatively about 6 ml of liquid containinga volatile material.

The reservoir 110 may include a bottom 114 and a single opening 116. Thereservoir 110 may also have a ridge 122 circumferencing the singleopening 116 or the upper edge of the reservoir 110. This ridge 122 mayprovide a generally flat surface upon which a rupturable substrate 120may be secured. The ridge 122 allows the secured area of the rupturablesubstrate 120 to be located away from the inner walls of the reservoir110 where the volatile material would be held.

It is contemplated that the method of the present invention may compriseproviding two or more reservoirs (not shown) which can be filled withthe same or different volatile materials. The reservoirs may have anyconfiguration that contacts the microporous membrane 140 upon rupture.For example, the reservoirs may be opposedly connected for use in aflippable device. In such a device the microporous membrane 140 isfluidly connected between the reservoirs.

Rupturable Substrate

Still referring to FIG. 2, the delivery engine 100 includes a rupturablesubstrate 120. The rupturable substrate 120 may be configured in anymanner that prevents the volatile material in the reservoir 110 fromcontacting the microporous membrane 140 prior to activating or rupturingthe delivery engine 100. In one embodiment, the rupturable substrate 120may enclose the reservoir, prior to activation, by extending across thesingle opening 116 securing to the ridge 122 of the reservoir 110. Therupturable substrate 120 may be secured by a layer of adhesives, heatand/or pressure sealing, ultrasonic bonding, crimping, and the like or acombination thereof.

The rupturable substrate 120 can be made of any material that ruptureswith applied force, with or without the presence of an element to aid insuch rupture. Because the rupturable substrate 120 is intended tocontain a volatile material while in storage, it may be made from anybarrier material that prevents evaporation of the volatile materialprior to its intended use. Such materials may be impermeable to vaporsand liquids. Suitable barrier materials for the rupturable substrate 120include a flexible film, such as a polymeric film, a flexible foil, or acomposite material such as foil/polymeric film laminate. Suitableflexible foils include a metal foil such as a foil comprised of anitrocellulose protective lacquer, a 20 micron aluminum foil, apolyurethane primer, and 15 g/m2 polyethylene coating (Lidfoil118-0092), available from Alcan Packaging. Suitable polymeric filmsinclude polyethylene terephtalate (PET) films, acrylonitrile copolymerbarrier films such as those sold under the tradename Barex® by INOES,ethylene vinyl alcohol, and combinations thereof. It is alsocontemplated that coated barrier films may be utilized as a rupturablesubstrate 120. Such coated barrier films include metallized PET,metalized polypropylene, silica or alumina coated film may be used. Anybarrier material, whether coated or uncoated, may be used alone and orin combination with other barrier materials.

Rupture Element

The rupturable substrate 120 may be breached to release a volatilematerial by actuating a rupture element 130. The rupture element 130 canbe injection, compression, or pressure molded using a polyolefin, suchas polyethylene or polypropylene; polyester; or other plastics known tobe suitable for molding. The rupture element 130 could also be made bythermoforming with a discrete cutting step to remove parts not wanted.

The rupture element 130 may be positioned in a space 132 formed in thedelivery engine body 104 that is adjacent to the rupturable substrate120 and subjacent a microporous membrane 140. The space 132 may beconfigured such that the rupture element 132 is nested within the spaceand enclosed by a microporous membrane 140, thus and requires no othermeans to hold the rupture element 132 in the delivery engine 100. In oneembodiment, the rupture element 130 is positioned between and in contactwith said rupturable substrate 120 and said microporous membrane 140. Arupture element 130 that is directly adjacent to the microporousmembrane 140 may facilitate wetting of the microporous membrane 140.More specifically, liquid may wick between rupture element 130 and themicroporous membrane 140 allowing for maintenance of a larger wettedsurface area of the microporous membrane 140.

The rupture element 130 may be configured in any manner such that a usercan manually actuate the rupture element 130 and breach the rupturablesubstrate 120 with relative ease. In one embodiment, a user may actuatethe rupture element 130 by manually compressing it. In otherembodiments, the rupture element 130 may be actuated and breach therupturable substrate 120 through contact with an element provided in adelivery engine housing that engages and compresses the rupture element130. Suitable compression forces to breach the rupturable substrate 120with a rupture element 130 may be less than about 25N, alternatively,less than about 20N, alternatively less than about 15N, alternativelyless than about 10N, alternatively less than about 5N, alternativelyfrom about 1N to about 15N, alternatively, from about 1N, to about 10N,alternatively, from about 1N to about 5N.

The compression force can be measured using an electromechanical testingsystem, QTest Elite 10, available from MTS, along with a modified UL 283finger probe made of polyamide. The UL 283 finger probe is described inStandard for Air Fresheners and Deodorizers, UL Standard 283, FIG. 10.1(UL Mar. 31, 2004). As described in UL 283, FIG. 10.1, the radius of thefinger tip is 3.5 mm; height of the finger tip is 5 mm; depth of thefinger tip is 5.8 mm. However, unlike the finger probe described in theaforementioned text, the modified UL 283 finger probe does not includeany articulating joints. Instead, it is in a fixed position that isperpendicular to the rupture element 130 when testing is conducted. Thetesting occurs at ambient temperatures (23±2° C.). The perimeter of adelivery engine 100 is rested on a support fixture, without directlycontacting or directly securing the rupture element 130 to the supportfixture. The crosshead speed of the electromechanical testing system isset at 30 mm/min. The modified UL 283 finger probe is moved towards therupture element 130 to contact a region where displacement is desiredfor rupturing a rupturable substrate 120. Where a flange 134 such as theone described herein is utilized, the desired region of displacement isthe mid-point of the flange 134. The mid-point is the point that is halfway between the proximal end and distal end 136. For example, where aflange 134 is 2 cm from proximal end to distal end 136, the mid-point islocated at 1 cm. The machine is run until the rupture element 130 isdisplaced by 6 mm. Zero displacement is defined as the point at which0.1N of force (i.e. preload) is applied. The load at the first peakwhere the rupturable substrate 120 is broken is recorded as the force torupture. Those of ordinary skill in the art will appreciate thatcompression forces will vary depending on the physical properties andplacement of the microporous membrane 140, rupture element 130, andrupturable substrate 120 in a delivery engine 100.

There are numerous embodiments of the rupture element 130 describedherein, all of which are intended to be non-limiting examples. FIG. 2shows one non-limiting embodiment of the rupture element 130. In thisembodiment, the rupture element 130 includes a flange 134 hinged to therupture element 130. The flange 134 may be injection molded and mayinclude a distal end 136. The distal end 136 may include one or morepiercing elements 138 located in the z-direction or towards therupturable substrate 120. In one embodiment, the distal end 136 mayinclude two spaced apart piercing elements 138 in the z-direction. In analternate embodiment, the distal end 136 may form a single point (notshown) along the x-y plane (not shown).

It is contemplated that the rupture element 130 may include more thanone flange 134 where additional points of rupture are desired. Forexample, the rupture element may include a first compressible flange anda second compressible flange opposedly hinged to said rupture element(not shown).

FIG. 3 shows another embodiment of a rupture element 330 which includesone or more piercing elements 332 supported on a correspondingspring-like part 334. The spring-like part 334 may be a metal coil,polyolefin or polyurethane foam, injection molded bristles, injectionmolded plastic spring or hinge parts, or the like. Upon pressing therupture element 330 towards the rupturable substrate 320, one or morepiercing elements 332 will puncture the rupturable substrate 320 andthen return to its original position. A user may manually compress orpress downward in the z-direction on the flange 134 such that therupturable substrate 120 is breached and a volatile material is releasedto the microporous membrane 140.

FIG. 4 shows another embodiment of a rupture element 430 where it isintegrally formed with the reservoir 410. This can be accomplished bythermoforming, pressure forming, injection molding or any known means offorming plastic parts. The rupture element 430 in this embodiment, is asharp piercing structure extending opposite from the interior bottom 414of the reservoir. A user may compress the bottom 414 of the reservoir410 to pierce the rupturable substrate 420 with the rupture element 430.This embodiment eliminates having to manufacture a separate ruptureelement 430, yet it performs the same function.

Collection Basin

Now referring to FIG. 5, the delivery engine 100 may optionally includea collection basin 112 to collect volatile materials from the reservoir110 after the rupturable substrate 120 is compromised. The collectionbasin 112 may be any size, shape or configuration, and may be made ofany suitable material, so long as it is in fluid communication with thereservoir 110 and the breathable membrane 140 upon rupturing therupturable substrate 120. It may be sized to collect any suitable volumeof a volatile material to provide a controlled volume of the volatilematerial to the breathable membrane 140. In one embodiment, thecollection basin 112 may be sized to collect about 1 ml to about 4 ml ofvolatile materials, alternatively about 1 ml to about 3 ml,alternatively about 1 ml to about 2.5 ml, alternatively about 1.5 ml toabout 1.8 ml.

In one embodiment, the collection basin 112 may include a bottom 118 inthe z-direction and a top that opens towards a breathable membrane 140.The breathable membrane 140 may lie across the open top, enclosing thecollection basin 112 so liquid cannot flow freely out through thebreathable membrane 140. The collection basin 112 may be integrallyconstructed with the body 104 of the delivery engine 100 in a thermoformpart.

As shown in FIG. 5, in one embodiment, the collection basin 112 ispositioned downwardly or opposite the y-direction from the reservoir110. When the delivery engine 100 is placed upright, a volatile materialnaturally flows down the reservoir 110 into the collection basin 112ensuring a controlled, continual dosing of the microporous membrane 140.Further, the collection basin 112 has depth along the z-axis which issmaller in depth than the reservoir 110, and the bottom 118 of thecollection basin lies closer to the microporous membrane 140 than thereservoir bottom 114. The proximity of the collection basin bottom 118with the microporous membrane 140 helps to ensure a continual supply ofvolatile material and wet more surface area of the microporous membrane140, even when very little volatile material remains in the deliveryengine 100. When the liquid contact area of the microporous membrane 140is greater, the evaporation rate of volatile materials is higher andfragrance intensity can be maintained over longer periods.

Membrane

The delivery engine 100 includes a microporous membrane 140. Themicroporous membrane 140 is vapor permeable and capable of wickingliquid, yet prevents free flow of liquid out of the membrane 140, thusaddressing leakage problems. The microporous membrane 140 enables thediffusion of the volatile materials to be controlled by evaporation ofthe liquid fragrance versus being dependent on the diffusion rates of aconventional polymer.

The microporous membrane 140 may be secured to the lip 102 of thedelivery engine 100 in the same manner as the rupturable substrate 120is sealed to the ridge 122 of the reservoir 110. The microporousmembrane 140 encloses the reservoir 110, rupturable substrate 120,rupture element 130, and collection basin 112. In this way, therupturable substrate 120 may be breached by compressing the microporousmembrane 140 and the rupture element 130. Once breached, the volatilematerial flows out of the reservoir 110, contacts the microporousmembrane 140, and is delivered to the atmosphere. Because themicroporous membrane 140 is shielded from the volatile material untilthe rupturable substrate is breached, the fragrance intensity may buildslowly from zero to its equilibrium rate of release when the microporousmembrane 140 is fully wetted.

The microporous membrane 140 of the present invention may have limitedselectivity leaving behind fewer perfume materials. Membranes that areselective, such as traditional polyethylenes, may inhibit high molecularweight volatile materials and materials with low solubility inpolyethylene from diffusing through. This may limit perfumeformulations, for example in the field of air fresheners where it istypically desired to use formulations having a wide variety of volatilematerials having different volatilities. For example, some membranes maypreclude the diffusion of alcohols, such as linalool and dihydromyrcenolwhich are widely used in perfume applications.

While not wishing to be bound by theory, the physical characteristics ofa membrane may affect the diffusion or transfer rate of volatilematerials through the membrane. Such characteristics may includematerials used, use of fillers, pore size, thickness, and evaporativesurface area.

As used herein, the “volatile material contact surface” is that surfaceof the microporous membrane that faces and typically is in contact withthe volatile material, which is, for example, contained in a testreservoir, as described in further detail below.

As used herein, the “vapor release surface” is that surface of themicroporous membrane that does not face and/or contact directly thevolatile material, and from which volatile material is released into anexterior atmosphere in a gaseous or vapor form.

As used herein, the term “(meth)acrylate” and similar terms, such as“esters of (meth)acrylic acid” means acrylates and/or methacrylates.

As used herein, the “volatile material transfer rate” of the microporousmembrane, was determined in accordance with the following description. Atest reservoir was fabricated from a clear thermoplastic polymer, havinginterior volume sufficient to contain 2 milliliters of volatile materialsuch as benzyl acetate. The interior dimensions of the reservoir wasdefined by a circular diameter at the edge of the open face ofapproximately 4 centimeters and a depth of no greater than 1 centimeter.The open face was used to determine the volatile material transfer rate.With the test reservoir laying flat (with the open face facing upward),about 2 milliliters of benzyl acetate was introduced into the testreservoir. With benzyl acetate introduced into the test reservoir, asheet of microporous membrane having a thickness of from 6 to 18 milswas placed over the open face/side of the test reservoir, such that 10cm² of the volatile material contact surface of the microporous membranewas exposed to the interior of the reservoir. The test reservoir wasweighed to obtain an initial weight of the entire charged assembly. Thetest reservoir, containing benzyl acetate and enclosed with the sheet ofmicroporous membrane, was then placed, standing upright, in a laboratorychemical fume hood having approximate dimensions of 5 feet (height)×5feet (width)×2 feet (depth). With the test reservoir standing upright,benzyl acetate was in direct contact with at least a portion of thevolatile material contact surface of the microporous membrane. The glassdoors of the fume hood were pulled down, and the air flow through thehood was adjusted so as to have 8 turns (or turnovers) of hood volumeper hour. Unless otherwise indicated, the temperature in the hood wasmaintained at 25° C.±5° C. The humidity within in the fume hood wasambient. The test reservoirs were regularly weighed in the hood. Thecalculated weight loss of benzyl acetate, in combination with theelapsed time and surface area of the microporous membrane exposed to theinterior of the test reservoir, were used to determine the volatiletransfer rate of the microporous membrane, in units of mg/(hour, cm²).

As used herein, the percent increase in volatile material transfer rateof the microporous membrane of the present invention from 25° C. to 60°C. was determined for separate but substantially equivalent microporousmembrane samples at 25° C. and 60° C., in accordance with the methoddescribed above. Reservoirs were placed in a large glass bell jar andover a 50% aqueous solution of potassium chloride also contained in thebell jar. The entire bell jar with contents was placed in an oven heatedto 60° C. The reservoirs were held under these conditions for a periodof 7 to 10 hours. The reservoirs were then returned to the hood atambient conditions overnight and the process was repeated over severaldays. Each of the reservoirs was weighed before being placed in the belljar and after being removed from the bell jar. Upon removal from thebell jar, the weight of each reservoir was taken after the reservoir hadreturned to ambient temperature.

As used herein, whether the vapor release surface of the microporousmembrane is “substantially free of volatile material in liquid form” wasdetermined in accordance with the following description. When the testreservoirs were weighed, as described above, the vapor release surfaceof the microporous membrane was examined visually by naked eye todetermine if drops and/or a film of liquid were present there-on. If anyevidence of drops (i.e., a single drop) and/or a film of liquid wasvisually observed on the vapor release surface, but did not run off thesurface, the microporous membrane was considered to be acceptable. Ifthe drops ran off the surface, the microporous membrane was determinedto have failed. If no evidence of drops (i.e., not one drop) and/or afilm of liquid was visually observed on the vapor release surface, themicroporous membrane was determined to be substantially free of volatilematerial in liquid form.

Transfer Rate

The volatile material transfer rate of the microporous membrane can beless than or equal to 0.7 mg/(hour*cm²), or less than or equal to 0.6mg/(hour*cm²), or less than or equal to 0.55 mg/(hour*cm²), or less thanor equal to 0.50 mg/(hour*cm²). The volatile material transfer rate ofthe microporous membrane can be equal to or greater than 0.02mg/(hour*cm²), or equal to or greater than 0.04 mg/(hour*cm²), or equalto or greater than 0.30 mg/(hour*cm²), or equal to or greater than 0.35mg/(hour*cm²). The volatile material transfer rate of the microporousmembrane may range between any combination of these upper and lowervalues. For example, the volatile material transfer rate of themicroporous membrane can be from 0.04 to 0.6 mg/(hour*cm²), or from 0.2to 0.6 mg/(hour*cm²), or from 0.30 to 0.55 mg/(hour*cm²), or from 0.35to 0.50 mg/(hour*cm²), in each case inclusive of the recited values.

While not intending to be bound by any theory, when volatile material istransferred from the volatile material contact surface to the vaporrelease surface of the microporous membrane, it is believed that thevolatile material is in a form selected from liquid, vapor, and acombination thereof. In addition, and without intending to be bound byany theory, it is believed that the volatile material, at least in part,moves through the network of interconnecting pores that communicatesubstantially throughout the microporous membrane.

Density and Coatings

The microporous membrane can have a density of at least 0.7 g/cm³, suchas at least 0.8 g/cm³. As used herein, the density of the microporousmembrane is determined by measuring the weight and volume of a sample ofthe microporous membrane. The upper limit of the density of themicroporous membrane may range widely, provided it has a targetedvolatile material transfer rate of, for example, from 0.04 to 0.6mg/(hour*cm²), and the vapor release surface is substantially free ofvolatile material in liquid form when volatile material is transferredfrom the volatile material contact surface to said vapor releasesurface. Typically, the density of the microporous membrane is less thanor equal to 1.5 g/cm³, or less than or equal to 1.2 g/cm³, or less thanor equal to 1.0 g/cm³. The microporous membrane can have a density offrom 0.7g/cm³ to 1.5 g/cm³, for example, from 0.8 g/cm³ to 1.2 g/cm³,inclusive of the recited values.

When the microporous membrane has a density of at least 0.7 g/cm³, suchas at least 0.8 g/cm³, the volatile material contact surface and thevapor release surface of the microporous membrane each may be free of acoating material thereon. When free of a coating material thereon, thevolatile material contact surface and the vapor release surface each aredefined by the microporous membrane.

When the microporous membrane has a density of at least 0.7 g/cm³, suchas at least 0.8 g/cm³, at least a portion of the volatile materialcontact surface of the microporous membrane, optionally, may have afirst coating thereon, and/or at least a portion of the vapor releasesurface of the microporous membrane, optionally, may have a secondcoating thereon. The first coating and the second coating may be thesame or different. When at least a portion of the volatile materialcontact surface has a first coating thereon, the volatile materialcontact surface is defined at least in part by the first coating. Whenat least a portion of the vapor release surface has a second coatingthereon, the vapor release surface is defined at least in part by thesecond coating.

The first coating and the second coating may each be selected fromliquid coatings and solid particulate coatings (e.g., powder coatings).Typically, each of the first and second coatings independently isselected from liquid coatings which may optionally include a solventselected from water, organic solvents and combinations thereof. Thefirst and second coatings each independently may be selected fromcrosslinkable coatings (e.g., thermosetting coatings and photo-curablecoatings), and non-crosslinkable coatings (e.g., air-dry coatings). Thefirst and second coatings may be applied to the respective surfaces ofthe microporous membrane in accordance with art-recognized methods, suchas spray application, curtain coating, dip coating, and/or drawn-downcoating (e.g., by means of a doctor blade or draw-down bar) techniques.

The first and second coating compositions each independently can includeart-recognized additives, such as antioxidants, ultraviolet lightstabilizers, flow control agents, dispersion stabilizers (e.g., in thecase of aqueous dispersions), and colorants (e.g., dyes and/orpigments). Typically, the first and second coating compositions are freeof colorants, and are as such substantially clear or opaque. Optionaladditives may be present in the coating compositions in individualamounts of from, for example, 0.01 to 10 percent by weight, based on thetotal weight of the coating composition.

The first coating and said second coating each independently can beformed from an aqueous coating composition that includes dispersedorganic polymeric material. The aqueous coating composition may have aparticle size of from 200 to 400 nm. The solids of the aqueous coatingcomposition may vary widely, for example from 0.1 to 30 percent byweight, or from 1 to 20 percent by weight, in each case based on totalweight of the aqueous coating composition. The organic polymers of theaqueous coating compositions may have number average molecular weights(Mn) of, for example, from 1000 to 4,000,000, or from 10,000 to2,000,000 .

The aqueous coating composition can be selected from aqueouspoly(meth)acrylate dispersions, aqueous polyurethane dispersions,aqueous silicone (or silicon) oil dispersions, and combinations thereof.The poly(meth)acrylate polymers of the aqueous poly(meth)acrylatedispersions may be prepared in accordance with art-recognized methods.For example, the poly(meth)acrylate polymers may include residues (ormonomer units) of alkyl(meth)acrylates having from 1 to 20 carbon atomsin the alkyl group. Examples of alkyl(meth)acrylates having from 1 to 20carbon atoms in the alkyl group include, but are not limited to,methyl(meth)acrylate, ethyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate,propyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate,isopropyl(meth)acrylate, butyl(meth)acrylate, isobutyl(meth)acrylate,tert-butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate,lauryl(meth)acrylate, isobornyl(meth)acrylate, cyclohexyl(meth)acrylate,and 3,3,5-trimethylcyclohexyl(meth)acrylate. For purposes ofnon-limiting illustration, an example of an aqueous poly(meth)acrylatedispersion from which the first and second coating compositions may eachbe independently selected is HYCAR 26138, which is commerciallyavailable from Lubrizol Advanced Materials, Inc.

The polyurethane polymers of the aqueous polyurethane dispersions, fromwhich the first and second coatings each independently may be selected,include any of those known to the skilled artisan. Typically thepolyurethane polymers are prepared from isocyanate functional materialshaving two or more isocyanate groups, and active hydrogen functionalmaterials having two or more active hydrogen groups. The active hydrogengroups may be selected from, for example, hydroxyl groups, thiol groups,primary amines, secondary amines, and combinations thereof. For purposesof non-limiting illustration, an example of an aqueous polyurethanedispersion from which the first and second coating compositions may eachbe independently selected is WITCOBOND W-240, which is commerciallyavailable from Chemtura Corporation.

The silicon polymers of the aqueous silicone oil dispersions may beselected from known and art-recognized aqueous silicone oil dispersions.For purposes of non-limiting illustration, an example of an aqueoussilicon dispersion from which the first and second coating compositionsmay each be independently selected is MOMENTIVE LE-410, which iscommercially available from Momentive Performance Materials.

The first coating and the second coating each independently can beapplied at any suitable thickness, provided the microporous membrane hasa targeted volatile material transfer rate of, for example, from 0.04 to0.6 mg/(hour*cm²), and the vapor release surface is substantially freeof volatile material in liquid form when volatile material istransferred from the volatile material contact surface to said vaporrelease surface. Also, the first coating and the second coating eachindependently can have a coating weight (i.e., the coating on themicroporous membrane) of from 0.01 to 5.5 g/m², such as from 0.1 to 5.0g/m², or from 0.5 to 3 g/m², or from 0.75 to 2.5 g/m², or from 1 to 2g/m².

The microporous membrane can have a density of less than 0.8 g/cm³, andat least a portion of the volatile material contact surface of themicroporous membrane can have a first coating thereon, and/or at least aportion of the vapor release surface of the microporous membrane canhave a second coating thereon. The first coating and the second coatingmay be the same or different, and each independently is as describedpreviously herein with regard to the optional first and second coatingsof the microporous membrane having a density of at least 0.7 g/cm³.

When less than 0.7 g/cm³, the density of the microporous membrane of thepresent invention may have any suitable lower limit, provided themicroporous membrane has a targeted volatile material transfer rate of,for example, from 0.04 to 0.6 mg/(hour*cm²), and the vapor releasesurface is substantially free of volatile material in liquid form whenvolatile material is transferred from the volatile material contactsurface to said vapor release surface. With this particular embodimentof the present invention, the density of the microporous membrane may befrom 0.6 to less than 0.8 g/cm³, or from 0.6 to 0.75 g/cm³ (e.g., from0.60 to 0.75 g/cm³) or from 0.6 to 0.7 g/cm³ (e.g., from 0.60 to 0.70g/cm³), or from 0.65 to 0.70 g/cm³.

Further, at least a portion of the volatile material contact surface ofthe microporous membrane can have a first coating thereon, and/or atleast a portion of the vapor release surface of the microporous membranecan have a second coating thereon, in which each of the first and secondcoatings independently is selected from a coating composition comprisinga poly(vinyl alcohol).

With the poly(vinyl alcohol) coated embodiment of the present invention,when the microporous membrane (i.e., the poly(vinyl alcohol) coatedmicroporous membrane) is exposed to a temperature increase of from 25°C. to 60° C., the volatile material transfer rate thereof increases byless than or equal 150 percent. When the poly(vinyl alcohol) coatedmicroporous membrane) is exposed to a temperature increase (e.g., froman ambient temperature of from 25° C. to 60° C.) the volatile materialtransfer rate typically increases, and typically does not decreaseunless, for example, the microporous membrane has been damaged byexposure to the higher ambient temperature. As such, and as used hereinand in the claims, the statement “the volatile material transfer ratethereof increases by less than or equal to [a stated] percent” (e.g.,150 percent), is inclusive of a lower limit of 0 percent, but is notinclusive of a lower limit that is less than 0 percent.

For purposes of illustration, when the poly(vinyl alcohol) coatedmicroporous membrane has a volatile material transfer rate of 0.3mg/(hour*cm²) at 25° C., when the microporous membrane is exposed to atemperature of 60° C., the volatile material transfer rate increases toa value that is less than or equal to 0.75 mg/(hour*cm²).

In an embodiment of the present invention, when the microporous membrane(i.e., the poly(vinyl alcohol) coated microporous membrane) is exposedto a temperature increase of from 25° C. to 60° C., the volatilematerial transfer rate thereof increases by less than or equal 125percent. For example, when the poly(vinyl alcohol) coated microporousmembrane has a volatile material transfer rate of 0.3 mg/(hour*cm²) at25° C., when the microporous membrane is exposed to a temperature of 60°C., the volatile material transfer rate increases to a value that isless than or equal to 0.68 mg/(hour*cm²).

Further, when the microporous membrane (i.e., the poly(vinyl alcohol)coated microporous membrane) is exposed to a temperature increase offrom 25° C. to 60° C., the volatile material transfer rate thereofincreases by less than or equal 100 percent. For example, when thepoly(vinyl alcohol) coated microporous membrane has a volatile materialtransfer rate of 0.3 mg/(hour*cm²) at 25° C., when the microporousmembrane is exposed to a temperature of 60° C., the volatile materialtransfer rate increases to a value that is less than or equal to 0.6mg/(hour*cm²).

The first and second poly(vinyl alcohol) coatings each independently maybe present in any suitable coating weight, provided the microporousmembrane has a targeted volatile material transfer rate of, for example,at least 0.04 mg/(hour*cm²), and when the microporous membrane (i.e.,the poly(vinyl alcohol) coated microporous membrane) is exposed to atemperature increase of from 25° C. to 60° C., the volatile materialtransfer rate thereof increases by less than or equal to 150 percent.Typically, the first poly(vinyl alcohol) coating and the secondpoly(vinyl alcohol) coating each independently have a coating weight offrom 0.01 to 5.5 g/m², such as from 0.1 to 4.0 g/m², or from 0.5 to 3.0g/m², or from 0.75 to 2.0 g/m².

The volatile material transfer rate of the poly(vinyl alcohol) coatedmicroporous membrane can be at least 0.02 mg/(hour*cm²). The volatilematerial transfer rate of the poly(vinyl alcohol) coated microporousmembrane may be equal to or greater than 0.04 mg/(hour*cm²), or equal toor greater than 0.1 mg/(hour*cm²), or equal to or greater than 0.2mg/(hour*cm²), equal to or greater than 0.30 mg/(hour*cm²), or equal toor greater than 0.35 mg/(hour*cm²). The volatile material transfer rateof the poly(vinyl alcohol) coated microporous membrane may be less thanor equal to 0.7 mg/(hour*cm²), or less than or equal to 0.6mg/(hour*cm²), or less than or equal to 0.55 mg/(hour*cm²), or less thanor equal to 0.50 mg/(hour*cm²). The volatile material transfer rate ofthe poly(vinyl alcohol) coated microporous membrane may range betweenany combination of these upper and lower values, inclusive of therecited values. For example, the volatile material transfer rate of thepoly(vinyl alcohol) coated microporous membrane can be at least 0.02mg/(hour*cm²), such as from 0.04 to 0.70 mg/(hour*cm²), or from 0.04 to0.60 mg/(hour*cm²), or from 0.20 to 0.60 mg/(hour*cm²), or from 0.30 to0.55 mg/(hour*cm²), or from 0.35 to 0.50 mg/(hour*cm²), in each caseinclusive of the recited values.

The density of the microporous membrane of the poly(vinyl alcohol)coated microporous membrane of the present invention may vary widely,provided that the poly(vinyl alcohol) coated microporous membrane has atargeted volatile material transfer rate, for example, of at least 0.04mg/(hour*cm²), and when the microporous membrane (i.e., the poly(vinylalcohol) coated microporous membrane) is exposed to a temperatureincrease of from 25° C. to 60° C., the volatile material transfer ratethereof increases by less than or equal to 150 percent.

Further, the density of the microporous membrane, of the poly(vinylalcohol) coated microporous membrane, may be at least 0.7 g/cm³, such asat least 0.8 g/cm³ (e.g., from 0.8 to 1.2 g/cm³) all inclusive of therecited values. In an embodiment of the present invention, the densityof the poly(vinyl alcohol) coated microporous membrane (i.e., thedensity of the microporous membrane prior to application of thepoly(vinyl alcohol) coating) is less than 0.8 g/cm³. For example, thedensity of the microporous membrane, of the poly(vinyl alcohol) coatedmicroporous membrane, may be from 0.6 to less than 0.8 g/cm³, or from0.6 to 0.75 g/cm³ (e.g., from 0.60 to 0.75 g/cm³) or from 0.6 to 0.7g/cm³ (e.g., from 0.60 to 0.70 g/cm³), or from 0.65 to 0.70 g/cm³, allinclusive of the recited values.

With the poly(vinyl alcohol) coated microporous membrane of the presentinvention, when volatile material is transferred from the volatilematerial contact surface to the vapor release surface, the vapor releasesurface is substantially free of volatile material in liquid form.

The poly(vinyl alcohol) coating may be selected from liquid coatingswhich may optionally include a solvent selected from water, organicsolvents and combinations thereof. The poly(vinyl alcohol) coating maybe selected from crosslinkable coatings (e.g., thermosetting coatings),and non-crosslinkable coatings (e.g., air-dry coatings). The poly(vinylalcohol) coating may be applied to the respective surfaces of themicroporous membrane in accordance with art-recognized methods, such asspray application, curtain coating, or drawn-down coating (e.g., bymeans of a doctor blade or draw-down bar).

In an embodiment of the present invention, the first and secondpoly(vinyl alcohol) coatings are each independently formed from aqueouspoly(vinyl alcohol) coating compositions. The solids of the aqueouspoly(vinyl alcohol) coating composition may vary widely, for examplefrom 0.1 to 15 percent by weight, or from 0.5 to 9 percent by weight, ineach case based on total weight of the aqueous coating composition. Thepoly(vinyl alcohol) polymer of the poly(vinyl alcohol) coatingcompositions may have number average molecular weights (Mn) of, forexample, from 100 to 1,000,000, or from 1000 to 750,000.

The poly(vinyl alcohol) polymer of the poly(vinyl alcohol) coatingcomposition may be a homopolymer or copolymer. Co-monomer from which thepoly(vinyl alcohol) copolymer may be prepared include those which arecopolymerizable (by means of radical polymerization) with vinyl acetate,and which are known to the skilled artisan. For purposes ofillustration, comonomers from which the poly(vinyl alcohol) copolymermay be prepared include, but are not limited to: (meth)acrylic acid,maleic acid, fumaric acid, crotonic acid, metal salts thereof, alkylesters thereof (e.g., C₂-C₁₀ alkyl esters thereof), polyethylene glycolesters thereof, and polypropylene glycol esters thereof; vinyl chloride;tetrafluoroethylene; 2-acrylamido-2-methyl-propane sulfonic acid and itssalts; acrylamide; N-alkyl acrylamide; N,N-dialkyl substitutedacrylamides; and N-vinyl formamide.

For purposes of non-limiting illustration, an example of poly(vinylalcohol) coating composition that may be used to form the poly(vinylalcohol) coated microporous membrane of the present invention, is CELVOL325, which is commercially available from Sekisui Specialty Chemicals.

The first and second poly(vinyl alcohol) coating compositions eachindependently can include art-recognized additives, such asantioxidants, ultraviolet light stabilizers, flow control agents,dispersion stabilizers (e.g., in the case of aqueous dispersions), andcolorants (e.g., dyes and/or pigments). Typically, the first and secondpoly(vinyl alcohol)coating compositions are free of colorants, and areas such substantially clear or opaque. Optional additives may be presentin the poly(vinyl alcohol) coating compositions in individual amounts offrom, for example, 0.01 to 10 percent by weight, based on the totalweight of the coating composition.

Matrix

The matrix of the microporous membrane is composed of substantiallywater-insoluble thermoplastic organic polymer. Such polymers suitablefor use as the matrix can widely vary. In general, any substantiallywater-insoluble thermoplastic organic polymer which can be extruded,calendered, pressed, or rolled into film, sheet, strip, or web may beused. The polymer may be a single polymer or it may be a mixture ofpolymers. The polymers may be homopolymers, copolymers, randomcopolymers, block copolymers, graft copolymers, atactic polymers,isotactic polymers, syndiotactic polymers, linear polymers, or branchedpolymers. When mixtures of polymers are used, the mixture may behomogeneous or it may comprise two or more polymeric phases.

Examples of classes of suitable substantially water-insolublethermoplastic organic polymers include thermoplastic polyolefins,poly(halo-substituted olefins), polyesters, polyamides, polyurethanes,polyureas, poly(vinyl halides), poly(vinylidene halides), polystyrenes,poly(vinyl esters), polycarbonates, polyethers, polysulfides,polyimides, polysilanes, polysiloxanes, polycaprolactones,polyacrylates, and polymethacrylates. Hybrid classes, from which thewater-insoluble thermoplastic organic polymers may be selected include,for example, thermoplastic poly(urethane-ureas), poly(ester-amides),poly(silane-siloxanes), and poly(ether-esters) are within contemplation.Further examples of suitable substantially water-insoluble thermoplasticorganic polymers include thermoplastic high density polyethylene, lowdensity polyethylene, ultra high molecular weight polyethylene(“UHMWPE”), polypropylene (atactic, isotactic, or syndiotactic),poly(vinyl chloride), polytetrafluoroethylene, copolymers of ethyleneand acrylic acid, copolymers of ethylene and methacrylic acid,poly(vinylidene chloride), copolymers of vinylidene chloride and vinylacetate, copolymers of vinylidene chloride and vinyl chloride,copolymers of ethylene and propylene, copolymers of ethylene and butene,poly(vinyl acetate), polystyrene, poly(omega-aminoundecanoic acid)poly(hexamethylene adipamide), poly(epsilon-caprolactam), andpoly(methyl methacrylate). The recitation of these classes and exampleof substantially water-insoluble thermoplastic organic polymers is notexhaustive, and are provided for purposes of illustration.

Substantially water-insoluble thermoplastic organic polymers may inparticular include, for example, poly(vinyl chloride), copolymers ofvinyl chloride, or mixtures thereof. In an embodiment thewater-insoluble thermoplastic organic polymer includes an ultrahighmolecular weight polyolefin selected from: ultrahigh molecular weightpolyolefin (e.g., essentially linear ultrahigh molecular weightpolyolefin) having an intrinsic viscosity of at least 10deciliters/gram; or ultrahigh molecular weight polypropylene (e.g.,essentially linear ultrahigh molecular weight polypropylene) having anintrinsic viscosity of at least 6 deciliters/gram; or a mixture thereof.In a particular embodiment, the water-insoluble thermoplastic organicpolymer includes UHMWPE (e.g., linear ultrahigh molecular weightpolyethylene) having an intrinsic viscosity of at least 18deciliters/gram.

UHMWPE is not a thermoset polymer having an infinite molecular weight,it is technically classified as a thermoplastic. However, because themolecules are substantially very long chains, UHMWPE softens when heatedbut does not flow as a molten liquid in a normal thermoplastic manner.The very long chains and the peculiar properties they provide to UHMWPEare believed to contribute in large measure to the desirable propertiesof microporous membranes made using this polymer.

As indicated previously, the intrinsic viscosity of the UHMWPE is atleast about 10 deciliters/gram. Usually the intrinsic viscosity is atleast about 14 deciliters/gram. Often the intrinsic viscosity is atleast about 18 deciliters/gram. In many cases the intrinsic viscosity isat least about 19 deciliters/gram. Although there is no particularrestriction on the upper limit of the intrinsic viscosity, the intrinsicviscosity is frequently in the range of from about 10 to about 39deciliters/gram. The intrinsic viscosity is often in the range of fromabout 14 to about 39 deciliters/gram. In most cases the intrinsicviscosity is in the range of from about 18 to about 39 deciliters/gram.An intrinsic viscosity in the range of from about 18 to about 32deciliters/gram is preferred.

The nominal molecular weight of UHMWPE is empirically related to theintrinsic viscosity of the polymer according to the equation:M(UHMWPE)=5.3×10⁴[η]^(1.37)where M(UHMWPE) is the nominal molecular weight and [η] is the intrinsicviscosity of the UHMW polyethylene expressed in deciliters/gram.

As used herein, intrinsic viscosity is determined by extrapolating tozero concentration the reduced viscosities or the inherent viscositiesof several dilute solutions of the UHMWPE where the solvent is freshlydistilled decahydronaphthalene to which 0.2 percent by weight,3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid, neopentanetetrayl ester[CAS Registry No. 6683-19-8] has been added. The reduced viscosities orthe inherent viscosities of the UHMWPE are ascertained from relativeviscosities obtained at 135.degree. C. using an Ubbelohde No. 1viscometer in accordance with the general procedures of ASTM D 4020-81,except that several dilute solutions of differing concentration areemployed. ASTM D 4020-81 is, in its entirety, incorporated herein byreference.

The matrix can comprise a mixture of substantially linear UHMWPE havingan intrinsic viscosity of at least 10 deciliters/gram, and lowermolecular weight polyethylene having an ASTM D 1238-86 Condition E meltindex of less than 50 grams/10 minutes and an ASTM D 1238-86 Condition Fmelt index of at least 0.1 gram/10 minutes. The nominal molecular weightof the lower molecular weight polyethylene (LMWPE) is lower than that ofthe UHMWPE. LMWPE is thermoplastic and many different types are known.One method of classification is by density, expressed in grams/cubiccentimeter and rounded to the nearest thousandth, in accordance withASTM D 1248-84 (re-approved 1989), as summarized in the following Table1.

TABLE 1 Type Abbreviation Density (g/cm³) Low Density Polyethylene LDPE0.910-0.925 Medium Density Polyethylene MDPE 0.926-0.940 High DensityPolyethylene HDPE 0.941-0.965Any or all of these polyethylenes may be used as the LMWPE in themicroporous membrane of the present invention. For some applications,HDPE may be used because it ordinarily tends to be more linear than MDPEor LDPE. ASTM D 1248-84 (Reapproved 1989) is, in its entirety,incorporated herein by reference.

Processes for making the various LMWPE's are well known and welldocumented. They include the high pressure process, the PhillipsPetroleum Company process, the Standard Oil Company (Indiana) process,and the Ziegler process. The ASTM D 1238-86 Condition E (that is,190.degree. C. and 2.16 kilogram load) melt index of the LMWPE is lessthan about 50 grams/10 minutes. Often the Condition E melt index is lessthan about 25 grams/10 minutes. Preferably the Condition E melt index isless than about 15 grams/10 minutes. The ASTM D 1238-86 Condition F(that is, 190.degree. C. and 21.6 kilogram load) melt index of the LMWPEis at least 0.1 gram/10 minutes. In many cases the Condition F meltindex is at least about 0.5 gram/10 minutes. Preferably the Condition Fmelt index is at least about 1.0 gram/10 minutes. ASTM D 1238-86 is, inits entirety, incorporated herein by reference.

Sufficient UHMWPE and LMWPE should be present in the matrix to providetheir properties to the microporous membrane. Other thermoplasticorganic polymer may also be present in the matrix so long as itspresence does not materially affect the properties of the microporousmembrane in an adverse manner. The other thermoplastic polymer may beone other thermoplastic polymer or it may be more than one otherthermoplastic polymer. The amount of the other thermoplastic polymerwhich may be present depends upon the nature of such polymer. Examplesof thermoplastic organic polymers which may optionally be presentinclude poly(tetrafluoroethylene), polypropylene, copolymers of ethyleneand propylene, copolymers of ethylene and acrylic acid, and copolymersof ethylene and methacrylic acid. If desired, all or a portion of thecarboxyl groups of carboxyl-containing copolymers may be neutralizedwith sodium, zinc, or the like.

The UHMWPE and the LMWPE together can constitute at least 65 percent byweight of the polymer of the matrix, such as at least 85 percent byweight of the polymer of the matrix, or the UHMWPE and the LMWPEtogether can constitute substantially 100 percent by weight of thepolymer of the matrix. The UHMWPE can constitute at least one percent byweight of the polymer of the matrix, and the UHMWPE and the LMWPEtogether constitute substantially 100 percent by weight of the polymerof the matrix.

Where the UHMWPE and the LMWPE together constitute 100 percent by weightof the polymer of the matrix of the microporous membrane, the UHMWPE canconstitute greater than or equal to 40 percent by weight of the polymerof the matrix, such as greater than or equal to 45 percent by weight, orgreater than or equal to 48 percent by weight, or greater than or equalto 50 percent by weight, or greater than or equal to 55 percent byweight of the polymer of the matrix. Also, the UHMWPE can constituteless than or equal to 99 percent by weight of the polymer of the matrix,such as less than or equal to 80 percent by weight, or less than orequal to 70 percent by weight, or less than or equal to 65 percent byweight, or less than or equal to 60 percent by weight of the polymer ofthe matrix. The level of UHMWPE comprising the polymer of the matrix canrange between any of these values inclusive of the recited values.

Likewise, where the UHMWPE and the LMWPE together constitute 100 percentby weight of the polymer of the matrix of the microporous membrane, theLMWPE can constitute greater than or equal to 1 percent by weight of thepolymer of the matrix, such as greater than or equal to 5 percent byweight, or greater than or equal to 10 percent by weight, or greaterthan or equal to 15 percent by weight, or greater than or equal to 20percent by weight, or greater than or equal to 25 percent by weight, orgreater than or equal to 30 percent by weight, or greater than or equalto 35 percent by weight, or greater than or equal to 40 percent byweight, or greater than or equal to 45 percent by weight, or greaterthan or equal to 50 percent by weight, or greater than or equal to 55percent by weight of the polymer of the matrix. Also, the LMWPE canconstitute less than or equal to 70 percent by weight of the polymer ofthe matrix, such as less than or equal to 65 percent by weight, or lessthan or equal to 60 percent by weight, or less than or equal to 55percent by weight, or less than or equal to 50 percent by weight, orless than or equal to 45 percent by weight of the polymer of the matrix.The level of the LMWPE can range between any of these values inclusiveof the recited values.

It should be noted that for any of the previously described microporousmembranes of the present invention, the LMWPE can comprise high densitypolyethylene.

Fillers

The microporous membrane may be filled with any suitable filler andplasticizer known in the art. Fillers may include finely-divided,substantially water-insoluble particulate filler material such as finelydivided silica, clays, zeolites, carbonates, charcoals, and mixturesthereof. The particulate filler material may include an organicparticulate material and/or an inorganic particulate material. Theparticulate filler material typically is not colored, for example, theparticulate filler material is a white or off-white particulate fillermaterial, such as a siliceous or clay particulate material.

The finely divided substantially water-insoluble filler particles mayconstitute from 20 to 90 percent by weight of the microporous membrane.For example, such filler particles may constitute from 20 to 90 percentby weight of the microporous membrane, such as from 30 percent to 90percent by weight of the microporous membrane, or from 40 to 90 percentby weight of the microporous membrane, or from 40 to 85 percent byweight of the microporous membrane, or from 50 to 90 percent by weightof the microporous membrane and even from 60 percent to 90 percent byweight of the microporous membrane.

In one embodiment the microporous membrane may be filled with about 50%to about 80%, by total weight, of silica, alternatively about 60% toabout 80%, alternatively about 70% to about 80%, alternatively about 70%to about 75%.

The finely divided substantially water-insoluble particulate filler maybe in the form of ultimate particles, aggregates of ultimate particles,or a combination of both. At least about 90 percent by weight of thefiller used in preparing the microporous membrane has gross particlesizes in the range of from 0.5 to about 200 micrometers, such as from 1to 100 micrometers, as determined by the use of a laser diffractionparticle size instrument, LS230 from Beckman Coulton, capable ofmeasuring particle diameters as small as 0.04 micron. Typically, atleast 90 percent by weight of the particulate filler has gross particlesizes in the range of from 10 to 30 micrometers. The sizes of the filleragglomerates may be reduced during processing of the ingredients used toprepare the microporous membrane. Accordingly, the distribution of grossparticle sizes in the microporous membrane may be smaller than in theraw filler itself.

Non-limiting examples of suitable organic and inorganic particulatematerials, that may be used in the microporous membrane of the presentinvention, include those described in U.S. Pat. No. 6,387,519 B1 atcolumn 9, line 4 to column 13, line 62, the cited portions of which areincorporated herein by reference.

In a particular embodiment of the present invention, the particulatefiller material comprises siliceous materials. Non-limiting examples ofsiliceous fillers that may be used to prepare the microporous membraneinclude silica, mica, montmorillonite, kaolinite, nanoclays such ascloisite available from Southern Clay Products, talc, diatomaceousearth, vermiculite, natural and synthetic zeolites, calcium silicate,aluminum silicate, sodium aluminum silicate, aluminum polysilicate,alumina silica gels and glass particles. In addition to the siliceousfillers, other finely divided particulate substantially water-insolublefillers optionally may also be employed. Non-limiting examples of suchoptional particulate fillers include carbon black, charcoal, graphite,titanium oxide, iron oxide, copper oxide, zinc oxide, antimony oxide,zirconia, magnesia, alumina, molybdenum disulfide, zinc sulfide, bariumsulfate, strontium sulfate, calcium carbonate, and magnesium carbonate.In a non-limiting embodiment, the siliceous filler may include silicaand any of the aforementioned clays. Non-limiting examples of silicasinclude precipitated silica, silica gel, fumed silica, and combinationsthereof.

Silica gel is generally produced commercially by acidifying an aqueoussolution of a soluble metal silicate, e.g., sodium silicate at low pHwith acid. The acid employed is generally a strong mineral acid such assulfuric acid or hydrochloric acid, although carbon dioxide can be used.Inasmuch as there is essentially no difference in density between thegel phase and the surrounding liquid phase while the viscosity is low,the gel phase does not settle out, that is to say, it does notprecipitate. Consequently, silica gel may he described as anon-precipitated, coherent, rigid, three-dimensional network ofcontiguous particles of colloidal amorphous silica. The state ofsubdivision ranges from large, solid masses to submicroscopic particles,and the degree of hydration from almost anhydrous silica to softgelatinous masses containing on the order of 100 parts of water per partof silica by weight.

Precipitated silica generally is produced commercially by combining anaqueous solution of a soluble metal silicate, ordinarily alkali metalsilicate such as sodium silicate, and an acid so that colloidalparticles of silica will grow in a weakly alkaline solution and becoagulated by the alkali metal ions of the resulting soluble alkalimetal salt. Various acids may be used, including but not limited tomineral acids. Non-limiting examples of acids that may be used includehydrochloric acid and sulfuric acid, but carbon dioxide can also be usedto produce precipitated silica. In the absence of a coagulant, silica isnot precipitated from solution at any pH. In a non-limiting embodiment,the coagulant used to effect precipitation of silica may be the solublealkali metal salt produced during formation of the colloidal silicaparticles, or it may be an added electrolyte, such as a solubleinorganic or organic salt, or it may be a combination of both.

Precipitated silicas are available in many grades and forms from PPGIndustries, Inc. These silicas are sold under the Hi-Sil® tradename.

For purposes of the present invention, the finely divided particulatesubstantially water-insoluble siliceous filler can comprise at least 50percent by weight (e.g., at least 65, at least 75 percent by weight), orat least 90 percent by weight of the substantially water-insolublefiller material. The siliceous filler may comprise from 50 to 90 percentby weight (e.g., from 60 to 80 percent by weight) of the particulatefiller material, or the siliceous filler may comprise substantially allof the substantially water-insoluble particulate filler material.

The particulate filler (e.g., the siliceous filler) typically has a highsurface area allowing the filler to carry much of the processingplasticizer composition used to produce the microporous membrane of thepresent invention. The filler particles are substantiallywater-insoluble and also can be substantially insoluble in any organicprocessing liquid used to prepare the microporous membrane. This canfacilitate retention of the particulate filler within the microporousmembrane.

The microporous membrane of the present may also include minor amounts(e.g., less than or equal to 5 percent by weight, based on total weightof the microporous membrane) of other materials used in processing, suchas lubricant, processing plasticizer, organic extraction liquid, water,and the like. Further materials introduced for particular purposes, suchas thermal, ultraviolet and dimensional stability, may optionally bepresent in the microporous membrane in small amounts (e.g., less than orequal to 15 percent by weight, based on total weight of the microporousmembrane). Examples of such further materials include, but are notlimited to, antioxidants, ultraviolet light absorbers, reinforcingfibers such as chopped glass fiber strand, and the like. The balance ofthe microporous membrane, exclusive of filler and any coating, printingink, or impregnant applied for one or more special purposes isessentially the thermoplastic organic polymer.

Pores

The microporous membrane of the present invention, also includes anetwork of interconnecting pores, which communicate substantiallythroughout the microporous membrane. On a coating-free, printing inkfree and impregnant-free basis, pores typically constitute from 35 to 95percent by volume, based on the total volume of the microporousmembrane, when made by the processes as further described herein. Thepores may constitute from 60 to 75 percent by volume of the microporousmembrane, based on the total volume of the microporous membrane. As usedherein and in the claims, the porosity (also known as void volume) ofthe microporous membrane, expressed as percent by volume, is determinedaccording to the following equation:Porosity=100[1−d ₁ /d ₂]where, d₁ is the density of the sample, which is determined from thesample weight and the sample volume as ascertained from measurements ofthe sample dimensions; and d₂ is the density of the solid portion of thesample, which is determined from the sample weight and the volume of thesolid portion of the sample. The volume of the solid portion of themicroporous membrane is determined using a Quantachrome stereopycnometer(Quantachrome Corp.) in accordance with the operating manualaccompanying the instrument.

The volume average diameter of the pores of the microporous membrane isdetermined by mercury porosimetry using an Autoscan mercury porosimeter(Quantachrome Corp.) in accordance with the operating manualaccompanying the instrument. The volume average pore radius for a singlescan is automatically determined by the porosimeter. In operating theporosimeter, a scan is made in the high pressure range (from 138kilopascals absolute to 227 megapascals absolute). If 2 percent or lessof the total intruded volume occurs at the low end (from 138 to 250kilopascals absolute) of the high pressure range, the volume averagepore diameter is taken as twice the volume average pore radiusdetermined by the porosimeter. Otherwise, an additional scan is made inthe low pressure range (from 7 to 165 kilopascals absolute) and thevolume average pore diameter is calculated according to the equation:d=2[v₁ r ₁ /w ₁ +v ₂ r ₂ /w ₂ ]/[v ₁ /w ₁ +v ₂ /w ₂]where, d is the volume average pore diameter; v₁ is the total volume ofmercury intruded in the high pressure range; v₂ is the total volume ofmercury intruded in the low pressure range; r₁ is the volume averagepore radius determined from the high pressure scan; r₂ is the volumeaverage pore radius determined from the low pressure scan; w₁ is theweight of the sample subjected to the high pressure scan; and w₂ is theweight of the sample subjected to the low pressure scan.

The microporous membrane of the present invention may have an averagepore size of about 0.01 to about 0.06 microns, alternatively from about0.01 to about 0.05 microns, alternatively about 0.01 to about 0.04,alternatively about 0.01 to about 0.03, alternatively about 0.02 toabout 0.04 microns, alternatively about 0.02 microns.

Generally on a coating-free, printing ink-free and impregnant-freebasis, the volume average diameter of the pores of the microporousmembrane is at least 0.02 micrometers, typically at least 0.04micrometers, and more typically at least 0.05 micrometers. On the samebasis, the volume average diameter of the pores of the microporousmembrane is also typically less than or equal to 0.5 micrometers, moretypically less than or equal to 0.3 micrometers, and further typicallyless than or equal to 0.25 micrometers. The volume average diameter ofthe pores, on this basis, may range between any of these values,inclusive of the recited values. For example, the volume averagediameter of the pores of the microporous membrane may range from 0.02 to0.5 micrometers, or from 0.04 to 0.3 micrometers, or from 0.05 to 0.25micrometers, in each case inclusive of the recited values.

In the course of determining the volume average pore diameter by meansof the above described procedure, the maximum pore radius detected mayalso be determined. This is taken from the low pressure range scan, ifrun; otherwise it is taken from the high pressure range scan. Themaximum pore diameter of the microporous membrane is typically twice themaximum pore radius.

Coating, printing and impregnation processes can result in filling atleast some of the pores of the microporous membrane. In addition, suchprocesses may also irreversibly compress the microporous membrane.Accordingly, the parameters with respect to porosity, volume averagediameter of the pores, and maximum pore diameter are determined for themicroporous membrane prior to application of one or more of theseprocesses.

Thickness and Surface Area

The microporous membrane may have a thickness in the z-direction, ofabout 0.01 mm to about 1 mm, alternatively between about 0.1 mm to 0.4mm, alternatively about 0.15 mm to about 0.35 mm, alternatively about0.25 mm.

Those of ordinary skill in the art will appreciate that the surface areaof the microporous membrane can vary depending on the user preferredsize of the delivery engine 100. In some embodiments, the evaporativesurface area of the microporous membrane may be about 2 cm² to about 100cm², alternatively about 2 cm² to about 35 cm², alternatively about 10cm² to about 50 cm², alternatively about 10 cm² to about 45 cm²,alternatively about 10 cm² to about 35 cm², alternatively about 15 cm²to about 40 cm², alternatively about 15 cm² to about 35 cm²,alternatively about 20 cm² to about 35 cm², alternatively about 30 cm²to about 35 cm², alternatively about 35 cm².

Suitable microporous membranes for the present invention include anUHMWPE-type membrane optionally filled with silica as described in U.S.Pat. No. 7,498,369. Such UHMWPE membranes include Daramic™ V5, availablefrom Daramic, Solupor®, available from DSM (Netherlands), and Teslin™SP1100HD, available from PPG Industries, and combinations thereof. It isbelieved that these membranes allow a volatile material to freelydissipate, while containing liquid within the delivery engine 100.

In one aspect of the invention, the microporous membrane may include adye that is sensitive to the amount of volatile material it is incontact with to indicate end-of-life. Alternatively, the microporousmembrane may change to transparent when in contact with a fragrance orvolatile material to indicate diffusion is occurring. Other means forindicating end-of-life that are known in the art are contemplated forthe present invention.

Housing

Now referring to FIGS. 6 to 9, the method of the present invention mayfurther comprise the step of providing a housing 200 for releasablyengaging the delivery engine 100. The housing 200 may comprise a width,length and depth along an x-axis, y-axis, and z-axis, respectively (asshown in FIG. 1). The housing 200 can be made of any suitable materialsuch as glass, ceramic, wood, plastic, composite material, etc, and canhave any size, shape and configuration suitable for encasing thedelivery engine 100. The housing 200 can be rigid or flexible and can bemade of material which allows the transfer of volatile materials to thesurrounding environment. The housing 200 may include a base 210, ahollowed core 240 supported on the base 210 and nested internally withina shell 220. The housing 200 may also include a notch 270 and vents 260.

Shell and Hollowed Core

As seen in FIGS. 8 and 9, the housing 100 may include a hollowed core240 supported on a base 210 and nested internally within a shell 220.The shell 220 may have a front wall 222 and a rear wall 224, both ofwhich may be generally coextensive with a front wall 242 and a rear wall244 of the hollowed core 240. The hollowed core 240 and shell 220 may beelliptically cylindrical and include a receiving end 230 for receivingthe delivery engine 100. The receiving end 230 may be disposed remotelyfrom the base 210 of the housing 200.

Ribs and Notches

The inner face of the rear wall 244 of the hollowed core 240 may includeone or more retaining ribs 246 for guiding the delivery engine 100downward into its final in-use position as seen in FIG. 9. In oneembodiment, the retaining ribs 246 may include a first retaining rib anda second retaining rib positioned on the inner face of the rear wall 244and which both extend longitudinally along the y-axis. The first andsecond retaining ribs may be positioned at the intersection of the front242 and rear walls 244 of the hollowed core 240 to receive the lip 102of the delivery engine 100.

The housing 200 may also include a notch 270, or a plurality of notches,to engage or compress the rupture element 130 as the delivery engine 100is being received in the housing 200. In this way, a user is notrequired to manually activate the delivery engine 100 prior to itsinsertion into the housing 200. The notch 270 may be configured in anymanner such that the delivery engine 100 can be inserted into thehousing 200 with relative ease while the notch 270 compresses therupture element 130 and breaches the rupturable substrate 120.

Suitable insertion forces to insert the delivery engine 100 whichcompresses the rupture element 130 and breaches the rupturable substrate120 include less than about 25N, alternatively less than about 20N,alternatively less than about 15N, alternatively less than about 5N,alternatively from about 1N to about 25N, alternatively from about 1N toabout 15N, alternatively from about 5N to about 20N, alternatively fromabout 5N to about 15N, alternatively about 8 to 15 N.

The insertion force can be measured using an electromechanical testingsystem, QTest Elite 10 available from MTS. The delivery engine 100 isclamped to the testing system and placed in the receiving end of thehousing without any force against any notch 270 or elements that breachor help breach the rupturable substrate 120. The crosshead speed of theelectromechanical testing system is set at 50 mm/min. The roomtemperature is 23±2° C. The machine is run until the rupturablesubstrate 120 is breached. Zero displacement is defined as the point atwhich 0.1N of force (i.e. preload) is applied. The load at the firstpeak where the rupture substrate 120 is broken is recorded as the forceto rupture. Those of ordinary skill in the art will appreciate thatinsertion forces will vary depending on the physical properties andplacement of the notch 270, microporous membrane 140, rupture element130, and rupturable substrate 120.

In one embodiment, the notch 270 may be laterally off-set from thecenter of the front wall 242 of the hollowed core 240, so that lessprojection of the notch 270 in the z-direction is required whenmanufacturing. Thus, the microporous membrane 140 does not need to bestretched as far, resulting in less likelihood of damage.

The notch 270 and ribs 246 are configured such that the delivery engine100 does not need to bend when inserting, resulting in lower insertionforce. As the delivery engine 100 is inserted into the housing 200, thenotch 270 compresses the microporous membrane 140 and the ruptureelement 130 in the direction of the reservoir 110 to breach therupturable substrate 120 and release volatile materials to themicroporous membrane 140. During insertion of the delivery engine 100,the ribs 246 guide the delivery engine 100 into contact and against thenotch 270, maintaining the lateral position of the delivery engine 100so the notch 270 fully engages the rupture element 130.

Vents

The housing 200 may have a plurality of vents 260 or apertures whichalign in a first, open position to facilitate delivery of the volatilematerial from the microporous membrane 140 to the atmosphere of the roomor rooms that require treatment. Increasing the effective size of thevents 260, may increase the delivery of volatile material. Conversely,decreasing the effective size of the vents 260, may decrease thedelivery of volatile material.

The vents 260 may be disposed anywhere on the housing 200. In theembodiment shown in FIGS. 6 to 9, the vents 260 are disposed on thefront walls 222, 242 of shell 220 and hollowed core 240. The numberand/or size of the vents 260 are not fixed. The size of the vents 260can be controlled by the user through a variety of means. A user mayopen, partially open, partially close, or close the one or more vents260 by sliding the shell 220 downwardly along the y-axis towards thebase 210 such that the desired amount of emission is delivered to thelocation needing treatment. The housing 200 may also be constructed toenable open and closing of the vents 260 by rotation of the shell 240around the x-axis (not shown). In addition to the vents 260, the housing200 may have other means for visual inspection of the delivery engine100.

The housing 200 may also include a clicking mechanism (not shown) tosignal to the user that the housing 200 is in the desired open or closedposition. Such clicking mechanism may include a first mating part (notshown) disposed along the outer face of the hollowed core 240 and asecond mating part (not shown) disposed along the inner face of theshell 220. The mating parts may frictionally engage the walls of theshell 220 and hollowed core 240 as they slide against one another. Whenthe desired open or closed position is reached the mating parts mayreleasably lock into place and may provide a clicking sound.

Volatile Material

The method of the present invention delivers a volatile material to theatmosphere in a continuous manner. The term “volatile material” as usedherein, refers to a material that is vaporizable at room temperature andatmospheric pressure without the need of an energy source. The volatilematerial may be a composition comprised entirely of a single volatilematerial. The volatile material may also be a composition comprisedentirely of a volatile material mixture (i.e. the mixture has more thanone volatile component). Further, it is not necessary for all of thecomponent materials of the composition to be volatile. Any suitablevolatile material in any amount or form, including a liquid or emulsion,may be used.

Liquid suitable for use herein may, thus, also have non-volatilecomponents, such as carrier materials (e.g., water, solvents, etc). Itshould also be understood that when the liquid is described herein asbeing “delivered”, “emitted”, or “released,” this refers to thevolatilization of the volatile component thereof, and does not requirethat the non-volatile components thereof be emitted.

The volatile material can be in the form of perfume oil. Mostconventional fragrance materials are volatile essential oils. Thevolatile material can be a volatile organic compound commonly availablefrom perfumery suppliers. Furthermore, the volatile material can besynthetically or naturally formed materials. Examples include, but arenot limited to: oil of bergamot, bitter orange, lemon, mandarin,caraway, cedar leaf, clove leaf, cedar wood, geranium, lavender, orange,origanum, petitgrain, white cedar, patchouli, neroili, rose absolute,and the like. In the case of air freshener or fragrances, the differentvolatile materials can be similar, related, complementary, orcontrasting.

The volatile material may also originate in the form of a crystallinesolid, which has the ability to sublime into the vapor phase at ambienttemperatures or be used to fragrance a liquid. Any suitable crystallinesolid in any suitable amount or form may be used. For example, suitablecrystalline solids include but are not limited to: vanillin, ethylvanillin, coumarin, tonalid, calone, heliotropene, musk xylol, cedrol,musk ketone benzohenone, raspberry ketone, methyl naphthyl ketone beta,phenyl ethyl salicylate, veltol, maltol, maple lactone, proeugenolacetate, evemyl, and the like.

It may not be desirable, however, for volatile materials to be toosimilar if different volatile materials are being used in an attempt toavoid the problem of emission habituation. Otherwise, the peopleexperiencing the emissions may not notice that a different material isbeing emitted. The different emissions can be provided using a pluralityof delivery systems each providing a different volatile material (suchas, musk, floral, fruit emissions, etc). The different emissions can berelated to each other by a common theme, or in some other manner. Anexample of emissions that are different but complementary might be acinnamon emission and an apple emission.

In addition to the volatile material of the present invention, thedelivery engine 100 may include any known malodor composition toneutralize odors. Suitable malodor compositions include cyclodextrin,reactive aldehydes and ionones.

While not wishing to be bound by theory, the continuous delivery of avolatile material may be a function of various factors includingmembrane pore size; membrane surface area; the physical properties of avolatile material, such as molecular weight and saturation vaporpressure (“VP”); and the viscosity and/or surface tension of thecomposition containing the volatile material.

The composition may be formulated such that the composition comprises avolatile material mixture comprising about 10% to about 100%, by totalweight, of volatile materials that each having a VP at 25° C. of lessthan about 0.01 torr; alternatively about 40% to about 100%, by totalweight, of volatile materials each having a VP at 25° C. of less thanabout 0.1 torr; alternatively about 50% to about 100%, by total weight,of volatile materials each having a VP at 25° C. of less than about 0.1torr; alternatively about 90% to about 100%, by total weight, ofvolatile materials each having a VP at 25° C. of less than about 0.3torr. In one embodiment, the volatile material mixture may include 0% toabout 15%, by total weight, of volatile materials each having a VP at25° C. of about 0.004 torr to about 0.035 torr; and 0% to about 25%, bytotal weight, of volatile materials each having a VP at 25° C. of about0.1 torr to about 0.325 torr; and about 65% to about 100%, by totalweight, of volatile materials each having a VP at 25° C. of about 0.035torr to about 0.1 torr. One source for obtaining the saturation vaporpressure of a volatile material is EPI Suite™, version 4.0, availablefrom U.S. Environmental Protection Agency.

Two exemplary compositions comprising a volatile material mixture havingvolatile materials of varying VPs are set forth below in Tables 2 and 3.These compositions are shown by way of illustration and are not intendedto be in any way limiting of the invention.

TABLE 2 Wt % Low VP (torr) High VP (torr) 27.71 0.14 0.325 20.78 0.08750.14 13.86 0.0625 0.0875 8.66 0.035 0.0625 8.66 0.014 0.035 6.93 0.008750.014 6.93 0.00625 0.00875 3.18 0.0035 0.00625 1.27 0.0014 0.0035 0.950.000875 0.0014 0.64 0.000625 0.000875 0.32 0.000375 0.000625 0.090.000175 0.000325

TABLE 3 Wt % Low VP (torr) High VP (torr) 33.38 0.14 0.325 25.75 0.08750.14 19.07 0.0625 0.0875 13.86 0.035 0.0625 4.00 0.014 0.035 1.500.00875 0.014 0.50 0.00625 0.00875 0.72 0.0035 0.00625 0.55 0.00140.0035 0.27 0.000875 0.0014 0.20 0.000625 0.000875 0.13 0.0003750.000625 0.07 0.000175 0.000325

The viscosity of a volatile material may control how and when it isdelivered to the microporous membrane 140. For example, less viscousvolatile materials may flow faster than the more viscous volatilematerials. Thus, the membrane may be first wetted with the less viscousmaterials. The more viscous volatile material, being slightly less or ofsimilar density with the less viscous phase, may remain in thecollection basin 112 via gravity. Thus, the less viscous volatilematerial may be delivered to the microporous membrane 140 and emitted tothe atmosphere more quickly. To help prevent liquid from seeping throughthe microporous membrane 140, volatile materials may have viscositiesless than about 23 cP and surface tension less than about 33 mN/m.

In one embodiment, the composition containing a volatile material mayhave a viscosity of about 1.0 cP to less than about 25 cP, alternativelyabout 1.0 cP to less than about 23, alternatively about 1.0 cP to lessthan about 15 cP.

The composition containing a volatile material may be designed such thatthe composition may include a surface tension of about 19 mN/m to lessthan about 33 mN/m, alternatively about 19 mN/m to less than about 30mN/m, alternatively about 19 mN/m to less than about 27 mN/m.

EXAMPLES

The following examples are not to be construed as limitations of thepresent invention since many variations thereof are possible withoutdeparting from its spirit and scope.

Example 1

In this example, two identical air freshening delivery engines aredesigned utilizing a Daramic V5 membrane with an evaporative surfacearea of approximately 34 cm². Two perfume compositions, RJJ-577 andRJJ-573-8, each having a volatile material mixture with volatilematerials of different VP ranges are tested in the air fresheningdelivery engines for evaporation rates. The VP ranges of the volatilematerials are shown in Tables 4 and 5.

TABLE 4 RJJ-577 VP VP 25° C. 25° C. Low High Wt % 0 0.001 0.2 0.001 0.010.0 0.01 0.1 3.4 0.1 0.3 28.6 0.3 10 64.8

TABLE 5 RJJ-573-8 VP VP 25° C. 25° C. Low High Wt % 0 0.001 1.9 0.0010.01 8.5 0.01 0.1 32.6 0.1 0.3 49.8 0.3 10 6.8

One delivery engine is loaded with 6000 mg of perfume compositionRJJ-577; the other with 6000 mg of perfume composition RJJ-573-8.RJJ-577 includes relatively higher VP components than RJJ-573-8. Eachfilled delivery engine is weighed; weight is recorded. Both deliveryengines are placed into housings and held in a room at 21° C. At thetimes indicated on FIG. 10, the delivery engine is weighed; weightrecorded. FIG. 10 shows that after about two weeks, the evaporation rateof RJJ-577 has almost flattened which would then require anotherdelivery engine. This would be costly and may be viewed as burdensome byconsumers. On the other hand, perfume RJJ-573-8 with a microporousmembrane delivers consistent linear intensity over a longer period oftime.

Example 2

In this example, two air freshening delivery engines are constructedutilizing different membranes. Each is tested for evaporation ratesusing RJJ-573-8, which was utilized in Example 1. 6000 mg of RJJ-573-8is loaded into a delivery engine with a low density polyethylenemembrane (LDPE) having an average pore size of about 40 microns. 6000 mgof RJJ-573-8 is loaded into a delivery engine having a Daramic V5microporous membrane. As can be seen from FIG. 11, the microporousmembrane is much more efficient in releasing the relatively low vaporpressure perfume than the LDPE membrane. Thus, utilizing a microporousmembrane in accordance with the present invention delivers higherintensities of lower vapor pressure (i.e. more pleasing “base note”perfume raw materials can be delivered).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural references unless the contentclearly dictates otherwise. Thus, for example, “a volatile material” mayinclude more than one volatile material

Every numerical range given throughout this specification will includeevery narrower numerical range that falls within such broader numericalrange, as if such narrower numerical range were all expressly writtenherein. For example, a stated range of “1 to 10” should be considered toinclude any and all subranges between (and inclusive of) the minimumvalue of 1 and the maximum value of 10; that is, all subranges beginningwith a minimum value of 1 or more and ending with a maximum value of 10or less, e.g., 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

Further, the dimensions and values disclosed herein are not to beunderstood as being strictly limited to the exact numerical valuesrecited. Instead, unless otherwise specified, each such dimension isintended to mean both the recited value and a functionally equivalentrange surrounding that value. For example, a dimension disclosed as “40mm” is intended to mean “about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed:
 1. A method of delivering a volatile materialcomprising the step of providing a delivery engine comprising: a. areservoir comprising a volatile material mixture, said volatile materialmixture comprising about 40% to about 100%, by total weight, of volatilematerials each having a vapor pressure at 25° C. of about 0.01 torr toabout 0.3 torr; b. a microporous membrane enclosing said reservoir, saidmicroporous membrane comprising an average pore size of about 0.01 toabout 0.03 microns: c. a rupturable substrate enclosing said reservoir;and d. a flow path between said rupturable substrate and saidmicroporous membrane e. a rupture element comprising a supportstructure, said rupture element and support structure positioned in saidflow path between said rupturable substrate and said microporousmembrane.
 2. The method of claim 1, wherein said volatile materialmixture comprises about 60% to about 90%, by total weight, of volatilematerials each having a vapor pressure at 25° C. of about 0.01 to about0.3 torr.
 3. The method of claim 1, wherein said volatile materialmixture comprises: a. 0% to about 15%, by total weight, of volatilematerials each having a vapor pressure at 25° C. of about 0.004 torr toabout 0.035 torr; b. about 0% to about 25%, by total weight, of volatilematerials each having a vapor pressure at 25° C. of about 0.1 torr toabout 0.325 torr; and c. about 65% to about 100%, by total weight, ofvolatile materials each having a vapor pressure at 25° C. of about 0.035torr to about 0.1 torr.
 4. The method of claim 1, wherein said volatilematerial mixture comprises a viscosity of about 1.0 cP to less thanabout 15 cP.
 5. The method of claim 1, wherein said volatile materialmixture comprises a surface tension of about 19 mN/m to less than about27 mN/m.
 6. The method of claim 1, wherein said microporous membranecomprises an average pore size of about 0.02 microns.
 7. The method ofclaim 1, wherein said volatile material mixture comprises a perfumematerial.
 8. The method of claim 1, wherein said delivery engine furthercomprises a collection basin in fluid communication with saidmicroporous membrane and said reservoir upon rupturing said rupturablesubstrate.
 9. The method of claim 1, wherein said microporous membraneencloses said rupturable substrate and said reservoir.
 10. The method ofclaim 1 further comprising the step of compressing said microporousmembrane and said rupture element to breach said rupturable substrate.11. The method of claim 1, wherein said method further comprises thestep of inserting said delivering engine in a housing, said housingcomprising a notch to compress said microporous membrane and saidrupture element.
 12. The method of claim 1, wherein said rupture elementcomprises a compressible flange.